Koczura Madeline, Martin Bruno, Musci Marilena, Massimo Martina Di, Bouchon Matthieu, Turille Germano, Kreuzer Michael, Berard Joel, Coppa Mauro
Université Clermont Auvergne, INRAE, VetAgro Sup, UMR1213 Herbivores, Saint-Genès-Champanelle, France.
Eidgenössische Technische Hochschule Zürich, Institute of Agricultural Sciences, Universitaetstrasse, Zurich, Switzerland.
Front Vet Sci. 2021 Jan 22;7:612504. doi: 10.3389/fvets.2020.612504. eCollection 2020.
In the mountains, autochthonous and robust breeds are often used to valorize biodiverse grasslands. Along with their lower nutrient requirements, compared to specialized dairy breeds, they are expected to be better adapted to complex environments and valorize grasslands into dairy products of high quality. Therefore, the aim of the present study was to investigate the grazing selection of three contrasting dairy breeds on a biodiverse mountain pasture, and its consequences on milk fatty acid (FA) profile and prevalence of individual terpenes. A dual-purpose breed from the Italian Alps, the Valdostana Red Pied (Va), was compared to Montbéliardes (Mo), more specialized in milk production, and the highly specialized Holsteins (Ho). Diet selection was measured by scan-sampling, calculating selectivity indexes, and collecting simulated bites during two consecutive days in June (end of first grazing cycle) and July (second grazing cycle). Milk samples were collected at each milking during these experimental periods. Yield of milk and its fat and protein contents were measured. Milk FA and terpenes were analyzed by gas chromatographic methods. We tested the effects of breed, period and their interaction in a repeated mixed model, and calculated Pearson's correlations between behavioral data and milk FA as well as terpenes. The Va grazed less mature vegetation than Ho, but this difference was not sufficient to lead to a major breed effect on milk FA profile and prevalence of terpenes. However, the proportion of α-linolenic acid (C18:3 n-3) was always higher in the milk fat of Va than Ho (Mo were intermediary), but this without any correlation to grazing selection. This could be a consequence from a different metabolism concerning ruminal biohydrogenation, but must be further investigated. Finally, we confirmed previous studies that highlighted a link between milk quality and cows' grazing behavior, but here without differences among breeds. All cows adapted their behavior to the herbage evolution during the season, leading to higher proportions of unsaturated FA in July than June milks. Our study suggests that under mountain grazing conditions (biodiverse pasture and cows in late lactation), milk quality depends more on herbage composition than on cow breed.
在山区，当地的强健品种常被用于提升生物多样性草原的价值。与专门的奶牛品种相比，它们的营养需求较低，预计能更好地适应复杂环境，并将草原转化为高品质的乳制品。因此，本研究的目的是调查三种不同奶牛品种在生物多样性山地牧场上的放牧选择，及其对牛奶脂肪酸（FA）谱和个别萜类物质含量的影响。将来自意大利阿尔卑斯山的兼用型品种瓦尔多斯塔纳红白花牛（Va）与更专门用于产奶的蒙贝利亚牛（Mo）以及高度专门化的荷斯坦牛（Ho）进行比较。通过扫描取样、计算选择性指数以及在6月（第一个放牧周期结束时）和7月（第二个放牧周期）连续两天收集模拟咬食情况来测量饮食选择。在这些实验期间，每次挤奶时采集牛奶样本。测量牛奶产量及其脂肪和蛋白质含量。通过气相色谱法分析牛奶中的脂肪酸和萜类物质。我们在重复混合模型中测试了品种、时期及其相互作用的影响，并计算了行为数据与牛奶脂肪酸以及萜类物质之间的皮尔逊相关性。Va牛啃食的植被比Ho牛成熟度低，但这种差异不足以导致品种对牛奶脂肪酸谱和萜类物质含量产生重大影响。然而，Va牛牛奶脂肪中α-亚麻酸（C18:3 n-3）的比例始终高于Ho牛（Mo牛介于两者之间），但这与放牧选择没有任何相关性。这可能是瘤胃生物氢化代谢不同的结果，但必须进一步研究。最后，我们证实了之前强调牛奶质量与奶牛放牧行为之间联系的研究，但在此处品种之间没有差异。所有奶牛都根据季节中牧草的变化调整了它们的行为，导致7月牛奶中不饱和脂肪酸的比例高于6月牛奶。我们的研究表明，在山区放牧条件下（生物多样性牧场和处于泌乳后期的奶牛），牛奶质量更多地取决于牧草组成而非奶牛品种。
